Solve for $a$. $a-15=4a-3$ $a=$
Solution: We need to manipulate the equation to get $ a $ by itself. $\begin{aligned} a-15&=4a-3 \\\\ a-15 {-4a} &= 4a-3{-4a} &&\gray{\text{Subtract 4a from each side.}}\\\\ -3a-15&=-3 &&\gray{\text{Combine like terms.}}\\\\ -3a-15{+15} &= -3{+15} &&\gray{\text{Add 15 to each side.}}\\\\ -3a &=12 &&\gray{\text{Combine like terms.}}\\\\ \dfrac{-3a}{{-3}} &= \dfrac{12}{{-3}} &&\gray{\text{Divide each side by -3.}}\\\\ a &= {-4} &&\gray{\text{Simplify.}} \end{aligned}$ The answer: $ a= { -4 }~~~~~~~~$ [Let's check our work!]